Device for determining deformations of motor vehicle components

ABSTRACT

A device for detecting a side impact of a vehicle an acceleration sensor provided in components of the vehicle and controlling a release of a side bag for protecting vehicle occupants, and a sensor for sensing a beginning of a plastic deformation of components provided on the components of the vehicle and reducing a release threshold for activation of the side bag.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a device for determining deformations of motor vehicle components.

[0002] The release point of a side bag in the case of side impact situations in the motor vehicles is mainly sensed by acceleration sensors. They are mainly located in the region of seat transverse supports, the sills in the door region, in particular B or C columns of the vehicle passenger compartment in a motor vehicle.

[0003] It has been determined with air pressure sensors that in the case of not side impact-caused pressure increases in the hollow spaces of the doors of the motor vehicles and in the case of exceeding of the sensitive first side bag release threshold, an undesired release of the side bag can occur. This can for example occur in the case of a sudden strike of the vehicle doors or release of the front bag.

[0004] In the case of a pile impact in the door center, the shortest side bag release times are required. During the release time the unobjectionable unfolding of a thorax side bag which is built in the vehicle and a side bag which is integrated in the seat back must be guaranteed, so that in this impact situations which can lead to dangerous injuries in the door center a maximum protection at the deformation-critical location is provided for the vehicle occupants. On the other hand, the non-release threshold of a side bag must be set at vehicle speeds between 20 and 25 km/h, to provide the required robustness of the sensor device against an undesirable release in the situations which are not critical for the vehicle occupants, substantially during sudden strikes of the vehicle doors.

[0005] A very fine parameter adjustment in the release algorithm of the air bag sensors in the hollow spaces of the vehicle doors leads in the case of the danger to desired short release times. On the other hand the release threshold is reduced to undesirable 10-15 km/h vehicle speed, which leads to above described disadvantages.

[0006] Pressure sensors in the case of pile impact in the center of a soft vehicle door from the point of view of rigidity have short response times, when compared with acceleration sensors arranged on the vehicle structure, however they have the above mentioned disadvantages. Pressure is a skalar variable, with which it is not important whether they originate from the vehicle interior (pressure build up by simultaneous release of both front air bags by door impacts with closed window/sliding roof surfaces) or from outside of the vehicle occupant compartment, for example in the case of a side impact on the vehicle.

SUMMARY OF THE INVENTION

[0007] Accordingly, it is an object of the present invention to provide a device for determining a deformations of motor vehicle components, which avoids the disadvantages of the prior art.

[0008] In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a device for detecting side impacts on a vehicle, wherein on the component of the vehicle, an element is provided which senses a beginning of a plastic component deformation and reduces a release threshold for activation of a side bag.

[0009] With the inventive device additionally to the evaluation of signals of peripheral acceleration sensors, the deformation of the door outer plate, for example the plastic door plate deformation is sensed by a stretching measuring strip sensor. The stretching measuring strip sensor is arranged in the hollow space between the motor vehicle door exterior and the motor vehicle door interior, for example on a door reinforcing element (tube, profile plate and the like). With the additional detection of the deformation of the door, the door impact can be recognized extremely fast, for example after 3-5 ms.

[0010] When additionally to the acceleration sensor, a stretching measuring strip sensor is provided for each vehicle door, the injury-causing side impact situation can be detected after 3-5 ms time interval. With the signal produced by the stretching measuring strip sensor the release threshold of the acceleration sensor provided for example on the B-column of a motor vehicle can be reduced, so that the side bag which protects the head and thorax region of the vehicle occupant can be activated in the correct time.

[0011] In the case of the use however of a sensor which responds to pressure, a lateral impact can be detected first after approximately 6 ms, with a blow time of the side bag of approximately 10 ms for the thorax side bag, which means half the detection time of a corresponding time interval with reference to the passive safety of the vehicle occupants.

[0012] In addition to the use in the hollow space of a vehicle door, the stretching measuring strip sensor in a comparible way can be also mounted in the front body region of a motor vehicle, for example on the front motor hood lower side, for foot impact recognition.

[0013] The stretching measuring strips can be riveted in advantageous manner to the deformation bodies whose elastic deformation start is to be sensed, so that the defective components can be easily exchanged, while the component to be monitored, for example a vehicle door can however remain to be used. For this purpose the stretching measuring strip sensor can be riveted simply to the reinforcing tube in the door hollow space so that an expensive direct welding or glueing on the deformation part can be dispensed with.

[0014] The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a view showing a driver or a co-driver door with a predetermined mounting position for a measuring strip sensor in accordance with the present invention;

[0016]FIG. 2 is a schematic view of an amplification circuit for the device in accordance with the present invention;

[0017]FIG. 3 is a view schematically showing a mounting principle of a stretching measuring strip sensor for the device in accordance with the present invention;

[0018]FIG. 4 is a side view of the stretching measuring strip sensor element with an arresting plug together with a plug tongs for device for present invention;

[0019]FIG. 5 is a plan view of the stretching measuring strip sensor of the inventive device shown in FIG. 4;

[0020]FIG. 6 is a view showing a configuration of the steel plate support for receiving sensor components of the inventive device; and

[0021]FIG. 7 is a side view of the steel plate support of the device in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022]FIG. 1 shows a view of a driver/co-driver door of a motor vehicle with a predetermined mounting position for a measuring strip sensor in the door interior on the reinforcing tube or reinforcing element. In FIG. 1 a motor vehicle component 1 is a vehicle door.

[0023] The vehicle door includes a door plate 2 and a recess 3 for the window plate. Reference numeral 4 identifies an A column region, reference numeral 5 identifies a B column region, and reference numeral 6 identify a door sill on the lower side of the vehicle door 1. A sensor element 8 formed as a stretching measuring strip sensor is arranged on the sensor position 7 substantially opposite to the center of the door plate 2 on the reinforcing element in the door interior. In the configuration shown in FIG. 1 the sensor element 8 which senses the deformation of the reinforcing element is a single stretching measuring strip element.

[0024] The sensor element 8 which is formed as a stretching measuring strip sensor is designed to be sensitive to stretching and bending in a micrometer region and has a k factor of approximately 2. This means that with 1% longitudinal change of the stretching measuring strip sensor, the resistance of the sensor element 8 changes by 2%. A very precise deformation-or in other words force measuring sensor can be realized with the stretching measuring strips. Moreover, the stretching measuring strip sensors make possible a one time longitudinal change of approximately 10%. The sensor elements 8 shown in FIG. 1 load a surface of approximately 0.1 cm², so that for a 10% longitudinal change at the stretching measuring strip sensor 8 a door reinforcing element deformation is required which extends far into the plastic region.

[0025] This means that a side bag release must take place before breaking of the stretching measuring strip sensor by exceeding the 10% longitudinal change.

[0026]FIG. 2 shows an evaluating circuit or an amplifying arrangement for the stretching measuring strip sensor. The deformation of the door reinforcing element can cause an elongation or bending of the sensing measuring strip sensor resistance 8. The substantial change of exceeding one or several thresholds is monitored in the release algorithm software of the air bag release device.

[0027] In contrast to the absolute weight sensing required for the passenger classification, for each impact recognition a dynamic measurement is sufficient. For this purpose the configuration of an amplifying circuit 10 in FIG. 10 is formed so that its amplifier 9 is formed as an alternating voltage amplifier. This is much simpler and less expensive than a direct voltage amplifier. The alternating voltage amplifier 9 is coupled through a hardware high pass with a suitable lower frequency. The exact lower cut-off frequency is adjusted with a higher and more accurately determinable software high pass.

[0028]FIG. 3 shows a structural principle of a stretching measuring strip sensor. A sensor element 8 is arranged on a door reinforcing element of a motor vehicle door. The door reinforcing element can be formed with different plate thicknesses. In modern personal motor vehicles the door plate thicknesses depending on the manufacture can vary between 0.5 nm and 1.0 nm. The sensor element 8 in accordance with FIG. 3 is arranged on a steel bottom support 12 which is formed as a steel plate bottom plate with a thickness of 0.5 mm and is covered by a synthetic plastic cover 32 shown in broken lines. The steel bottom support 12 is mounted by a separable mounting in form of rivets, releasably on the door reinforcing element in the hollow space of a motor vehicle door. This mounting type has the advantage that a defective sensor element 8 can be removed from its mounting position 7 in the door interior, while the component 1 for example a motor vehicle door can further remain in operation, and in the case of the defective sensor no exchange of the complete component 1 or 12 is required.

[0029] A plate 20 is mounted on the steel bottom plate 12. A plurality of electronic components in form of ceramic chip capacitors 27, connecting elements 13 as well as an evaluating block identified with reference numeral 16 are arranged on an upper side 19 of the plate 20. The mounting of the plate 20, of the electronic elements as well as the electronic components on the plate 20 on a thin steel plate support 12 is required to realize on the sensor element 8 the required bending property which must be little influenced during the bending of the door reinforcing element 11.

[0030]FIG. 4 shows the side view of a stretching measuring strip sensor element with a plug connection element 17 engaged on a steel support 12 and with plug prongs 13 arranged on it. The sensor element 8 in accordance with FIG. 1 analogously to the sensor element of FIG. 3, is mounted by separable mounting rivets 15 on the side of a door reinforcing element. The steel bottom plate 12 is for example 0.5 mm thick and receives a printed circuit board 20 on its upper side, which is mounted with a temperature-resistant adhesive 28 on the upper side of the steel bottom plate 12. The flex printed circuit board 20 is composed of a Capton foil 25. It serves as a component and connecting conductor support for the measuring strip sensor, which can be formed as a NiCr or constantan layer and welded on the steel bottom plate 12 on an insulating layer. The flex printed circuit board serves furthermore as a carrier for the evaluating block 16 and a number of discreet ceramic chip capacitors 27.

[0031] The height of the structure of the sensor arrangement 8 from the door reinforcing element to the upper side of the cover 32 which covers the switching device, amounts to only a few mm as identified with reference numeral 30. In the embodiment of FIG. 4 it amounts to approximately 6 mm. In the region of the plug element 17 which is arranged with two arresting projections 21 of the upper side of the steel bottom plate, the total height identified with reference numeral 31 amounts to approximately 18 mm. The plug tongs 13 which in the region of their extension through the plug 17 are identified with a broken line, are connected with the printed circuit board 20 which receives the electronic components by a reflow solder connection 26.

[0032] After sputtering of the stretching measuring strip sensor on the Capton foil 20 and its glueing by the temperature-resistant adhesive connection 28 on the steel bottom plate 12, the electronic components and both plug tongs 13 are contacted in a single reflow soldering step 26. The plug housing 17 is arrested with the steel bottom plate 12 in an advantageous manner with the injected arresting projections 21. Between the door reinforcing element and the lower side of the steel bottom plate 12, because of the deep-drawn cavern in the steel bottom 12, a sufficient space for the plug arresting projections is provided as can be seen from FIG. 7.

[0033] The synthetic plastic cover 33 of the stretching measuring strip sensor 8 is engaged for example only on the plug housing 17. In order to guarantee the water tightness against spraying water or against rain water which enters through a door seal, the cover 33 is glued circumferentially with an adhesive 28 to the steel bottom plate 12 which is mounted on the door reinforcing element by rivets 15.

[0034]FIG. 5 shows the plan view of the sensor element 8 of FIG. 4. In this configuration the openings 22 are positioned so that the stretching measuring strip sensor 8 can be separably connected with the door reinforcing element 11 by the rivits 15 which extend through them.

[0035]FIG. 5 shows the course of the adhesive seam 28 for protecting the electronic component 16 or 27 from penetration of moisture. The plug tongs 13 are shown in a broken line and injected in the plug 17 engaged with the steel bottom plate 12. Reference numeral 23 identifies in FIG. 5 a stretching measuring strip resistor. The meander orientation extends parallel to the longitudinal axis of the door deformation element 11, so that its bending in direction of the vehicle inner space can be measured.

[0036] The use of a Capton foil 20 as a flex printed circuit board, the formation of the steel bottom plate 12 as a thin-wall bottom plate with a material thickness of only 0.5, as well as a thin-wall cover 32 mounted in extremely low height guarantees the required ductility as well as the low bending property of the stretching measuring strip sensor 8 in accordance with the embodiments shown in FIGS. 3 and 4. It is therefore guaranteed that the own rigidity of the stretching measuring strip sensor component 8 does not falsify the deformation condition of the deformation support.

[0037]FIG. 6 shows a plan view of a correspondingly configurated steel bottom plate 12. Reference numerals 18 identify the openings in the steel bottom plate with 0.5 mm thickness, in which the arresting projections 21 of the plug element 17 can be arrested. The plate 20 shown in FIGS. 4 and 5 is formed as a flexible Capton foil and supports the individual electronic components. In accordance with the opening pattern of openings in FIG. 6, two openings 22 are provided for mounting of the steel bottom plate 12 on the door reinforcing element 11. Therefore, with a corresponding number of rivets 15, the steel bottom plate together with the plate 20 can be mounted in a hollow space of a motor vehicle door.

[0038] Such riveted deformation sensors 8 provide for a possibility of occupant protection improvement in the case of side impacts and substantially reduce the injury risk of the vehicle occupants. A sensor element 8 in accordance with the present invention which detects the deformation of the motor vehicle components, can be arranged in a similar way also on a front motor hood region of a motor vehicle and serves for foot area impact recognition. It is possible to separably arrange deformation sensors for foot area impact recognition as contact sensors on a bumper support in the front region of the motor vehicle, to measure around a bending axis and to be connected just with two rivets.

[0039] The mounting of the inventive stretching measuring strip sensor element 8 with the use of two rivets is considered in the automobile industry as especially advantageous since the rivet connection in the interior of the door represents today a conventional and usable mounting type in automobile manufacture. Moreover, the stretching measuring strips can be only riveted and not screwed, since the screw connection over its service life can loose a tightening force. In advantageous manner in accordance with the present invention the stretching measuring strip sensor can be simply exchanged. In the case of mounting proposed here, the stretching measuring strip sensor is not glued or welded with the door reinforcing element, since otherwise in the case of defective stretching measuring strip sensor element 8 the total component, or in other words a vehicle door must be exchanged.

[0040] Advantageously the stretching measuring strip 23 is directly welded on the steel bottom plate 12 and its both connecting points are contacted on the flex printed circuit board 20 with two bonds 25. Therefore the creep effect with the glued stretching measuring strip elements is avoided. The printed circuit board 20 is correspondingly cut at the side of the stretching measuring strip sensor element 23 in FIG. 5.

[0041] It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

[0042] While the invention has been illustrated and described as embodied in device for determining deformations of motor vehicle components, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

[0043] Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. 

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:
 1. A device for detecting a side impact of a vehicle, comprising acceleration sensitive means provided in components of the vehicle and controlling a release of a side bag for protecting vehicle occupants; and means for sensing a beginning of a plastic deformation of components provided on the components of the vehicle and reducing a release threshold for activation of the side bag.
 2. A device as defined in claim 1, wherein said means for sensing the plastic deformation include stretching measuring strip sensors which have an output signal reducing the releasing threshold of the acceleration sensor provided in the vehicle.
 3. A device as defined in claim 2, wherein said stretching measuring strip sensor has a single meandering resistance whose amount change on exceeding one or several threshold is monitored.
 4. A device as defined in claim 3, wherein said resistance is oriented so that it measures a longitudinal change of the component to be monitored.
 5. A device as defined in claim 3; and further comprising a steel bottom plate on which said resistance is welded and connected to the component by a rivet connection.
 6. A device as defined in claim 5; and further comprising a printed circuit board; a base plate provided on the printed circuit board and carrying an evaluating block and a number of electronic components, said base plate being connectable to an inner side of the deformable components through a releasable mounting element.
 7. A device as defined in claim 2; and further comprising an alternating current amplifier which amplifies the output signal of said stretching measuring strip sensor.
 8. A device as defined in claim 7; and further comprising a base plate which does not influence a deformation of the component and is bendable, said measuring strip sensor and said amplifier being arranged on said base plate.
 9. A device as defined in claim 6, wherein said base plate has an upper side on which said flexible printed circuit board is provided as a connection conductor support for said measuring strip sensor, said evaluating block and said electronic components. 